It's somewhat understandable for some players, especially if they're injury prone and/or injured this year, as Gary was. For Grier, in particular, I don't really get it, though he is apparently projected higher than I expected despite his size and lack of games against good defenses.
Conversely, some coaches are guilty of not playing their seniors as much in bowl games in favor of returning players, so coaches can't necessarily play the victim role, either.